This invention relates to testing of a rotary movement-electrical signal transducer system, and more particularly, to apparatus and a method for dynamic testing of a rotary movement-electrical signal transducer system.
Automobiles are currently being produced with anti-block or anti-skid systems to control skidding. Such an anti-block system typically includes a rotary movement-electrical signal transducer subsystem associated with each wheel of the automobile, a computer controller, and an electrical signal-brake pressure transducer subsystem associated with each brake of the automobile. Each rotary movement-electrical signal transducer subsystem supplies an electrical signal which is in pulses frequency-related to the rotary movement of a wheel. These signals are read and interpreted by the computer controller, which, when a skid is indicated during braking of the automobile, signals the electrical signal-brake pressure transducer subsystems to reduce braking of the skidding wheels and thereby counteract the skid.
In at least one such system, the rotary movement-electrical signal subsystem includes a toothed ferromagnetic wheel co-axially mounted with the wheel of the automobile. A magnetic-electric transducer or sensor is fixedly mounted adjacent the ferromagnetic wheel, where the teeth and interposing gaps of the ferromagnetic wheel co-operate with the sensor to generate a sinusoidal electrical signal. The frequency of the signal is proportional to the rotational velocity of the ferromagnetic wheel and thus the rotational velocity of the automobile wheel.
A problem associated with a rotary movement-electrical signal transducer subsystem or system as described is accurate testing of the system. Erroneous electrical signals may be caused by many component failures, including teeth missing from the toothed wheel. Since the toothed wheel and sensor are typically located within a sealed chamber behind the vehicle wheel, remote electronic testing on the subsystem is desirable. U.S. Pat. No. 4,092,853 discloses a basic test system and method, but this system and method fail to indicate the absence of teeth unless three adjacent teeth are missing.